The heterojunction of single-wall carbon nanotubes (SWCNTs) and perovskite quantum dots (QDs) shows excellent photodetection performances due to the combination of the advantages of high carrier mobility of SWCNTs and high absorption coefficient of perovskite QDs. However, the band structure of a SWCNT is determined by its atomic arrangement structure. How the structure of SWCNTs affects the photoelectric performance of the composite film remains elusive. Here, we systematically explored the diameter effect of SWCNTs with different bandgaps on the photodetection performances of SWCNTs/perovskite QDs heterojunction films by integrating semiconducting SWCNTs (s-SWCNTs) with different diameters with CsPbBr₃ QDs. The results show that with an increase in diameter of s-SWCNTs, the heterojunction exhibits increasing responsivity (R), detectivity (D*), and faster response time. The great improvement in the optoelectronic performances of devices should be attributed to the higher carrier mobility of larger-diameter SWCNT films and the increasing built-in electric field at the heterojunction interfaces between larger-diameter SWCNTs and CsPbBr₃ QDs, which enhances the separation of the photogenerated excitons and the transport of the resulted carriers in SWCNT films.

Increasing the concentration of single-wall carbon nanotubes (SWCNTs) is an effective method for enhancing their luminescence intensity. However, an increase in the concentration of SWCNTs would inevitably increase their reabsorption effect, degrading their luminescence efficiency. Herein, we systematically investigated variations in the photoluminescence (PL) intensity of (6,5) single-chirality SWCNTs while increasing their concentration. The results show that the PL intensity first increased to a maximum and then decreased with increasing concentration. Numerical analysis indicates that the concentration boundary corresponding to the maximum PL intensity was strongly dependent on the ratio of the optical absorbances of the SWCNTs at their excitation and emission wavelengths. According to this, statistical analysis by experimentally measuring the optical absorption spectra of 18 kinds of single-chirality SWCNTs shows that the concentration boundaries of SWCNTs were dependent upon their Types and diameters. The concentration boundary of Type I SWCNTs was higher than that of Type II SWCNTs, and the concentration boundaries of both Types increased with increasing diameter. These results provide important guidance for spectral characterization and applications in bioimaging and photoelectronic devices.

Bulk synthesis of single-walled carbon nanotubes (SWNTs) using solid catalyst has been challenging, despite of recent breakthrough in the chirality-specific growth on the flat substrate surface. In this work, we propose a porous magnesia support rhenium catalyst for bulk synthesis of SWNTs. It is found that the well-dispersed catalyst with a high melting point and the optimal chemical vapor deposition reaction conditions account for the growth of SWNTs. Detailed characterizations reveal the produced SWNTs are dominant in (n, n − 1) and (n, n − 2) species. Furthermore, by using a multicolumn chromatography post-growth separation method, SWNTs with three defined diameter ranges were obtained. This work guides the design of porous oxide supported catalyst for bulk synthesis and diameter-dependent sorting of SWNTs, which will ultimately help harness the extraordinary properties of SWNTs.

In this work, we quantitatively studied the intertube coupling of different (n, m)-sorted semiconducting single-wall carbon nanotubes (SWCNTs) on their photoluminescence (PL) efficiencies by precisely tuning the ratio of (9, 4) and (6, 5) SWCNTs in the mixture. A significant decrease in the PL intensity of (9, 4) SWCNTs was observed after mixing with (6, 5) species when fixing the (9, 4) concentration, which was confirmed to be caused by the absorption of incident photons and reabsorption of the emitted photons by the added (6, 5) species. By contrast, a similar decrease in the PL intensity of (6, 5) SWCNTs was also observed after mixing with the larger-diameter (9, 4) species. Different from that of (9, 4) SWCNTs, the PL decrease of (6, 5) SWCNTs was found to originate not only from photon absorption and reabsorption by the (9, 4) species but also from one-way exciton energy transfer (EET) from the (6, 5) SWCNTs to the larger-diameter (9, 4) SWCNTs. Both the experimental results and numerical simulations further demonstrated that increasing the concentration of mixed (9, 4) SWCNTs would enhance the effects of photon absorption and reabsorption and EET on the PL intensity of (6, 5) SWCNTs quantified by the decrease ratio of the (6, 5) PL intensity. Meanwhile, the influence of EET was found to be always weaker than that of photon absorption and reabsorption. We proposed that the observed EET between isolated SWCNTs in a surfactant solution is derived from their proximity due to Brownian motion.